THE CR1NO1DEA 



143 



Dicyclic Inadunata caiue to their acme in Carboniferous times, and only 

 those forms persisted to Neozoic and Recent periods which assumed an 

 Articulate modification, viz. a loose lateral union of proximal brachials, 

 as seen in Pentacrinidae, which are convergents of the Neozoic Flexibilia. 

 The latter sub -order was represented during Palaeozoic times by the 

 Ichthyocrinoidea (Impinnata) ; between them and the Neozoic Apio- 

 crinidae, Bourgueticrinidae, etc. (Pinnata), the links are missing, but may 

 yet be found among Permian and Triassic crinoids (cf. p. 140). At any 

 rate, the Neozoic Flexibilia, when they assumed the free-swimming habit, 

 took a new lease of life and have their acme in our own day. 



The systematic account of the Crinoidea may be prefaced .by a table 

 of the terms and symbols employed in technical description, as explained 

 for the most part in the preceding pages. 



PLATES OF PATINA ..... Seepage 112 



Infrabasal . . .IB . . ,,99 



Basal . . . B , . . 99 



Superbasal . . SB ., ,, 159 



Radial. . . . R 



Inferradial Ri 



Superradial . . R . . 



Radianal . . RA . 



Pararadial . PR 



BRACHIALS . . free, Br ; fixed, Br . 



Primibrachs . . ,, IBr ,. IBr . 



First primibrach . IBr, 



Second primibrach . IBr 2 i ; 



Primaxil . ?. ,,. . I Ax 



Secundibrachs . . IIBr ,, IIBr . 



Secundaxil . . IIAx 



Tertibrachs . . . IIIBr 



Quartibrachs . . IVBr 



and so on to the 



Finials . F 



AMBULACRALS . . . Amb or c. p. 



Primambulacs . . I Amb 



Secundambulacs . . IIAmb . 



and so on. 

 INTERRADIAL AND SUPPLEMENTARY 



ELEMENTS 



Ai^ interradius . . IR 



Interbrachials . . . jBr 



Intersecundibrachs . illBr 



ana so on. 

 Special anal plate (or proximal 



median plate of anal tube) . x 

 Proximal tube -plate on right . rt 

 Corresponding plate on left . It 

 Deltoids . . .A 



here regarded as homologous with 

 Orals O 



Interambulacrals . . iAmb 



Interprimambulacs . ilAmb 



Intersecundambulacs . illAmb . 



The various radii and interradii are denoted as explained in the table 

 on p. 110. 



112 



112 



119 



150 



100, 112 



114 



115 



115 



114 



114 



114 



114 



114 



115 



100, 115 

 115 

 115 



109 



20 



118 



118 



119 

 121 

 121 

 100 



124 

 118 

 118 

 118 



